Evaluating the effect of pile spacing and configuration on the lateral resistance of pile groups

In this study, the effects of pile spacing and pile group (PG) configuration on the static lateral resistance of PGs are investigated using finite element (FE) numerical modeling. Three-dimensional FE models for a 4 x 4 vertical, battered, and mixed PG configurations were developed and analyzed at three pile spacings (3D, 5D, 7D) and for three clay soils (soft, medium, stiff). The nonlinear pile and soil behaviors were accounted for using elastoplastic constitutive models and a pile-soil interface model. The effects of pile spacing and configuration on the group efficiency, axial reaction in piles, and p-multipliers are discussed. The results showed that the battered PG had the largest group efficiency followed by mixed PG and then vertical PG at all pile spacings. The axial reaction in piles decreased only in two pile rows when the pile spacing increased in the three PGs. The back-calculated p-multipliers were different between the PGs with the largest values in the battered PG. Modifications to the p-multipliers used in practice are proposed to account for the effect of configuration in the battered and mixed PGs.